Category Archives: Drug Safety Education

Understanding Syringes

Types of Syringes

  1. Insulin. Most people who inject drugs (PWID) use insulin syringes. They come in one piece (with permanently attached needles) and usually have orange caps.
Two insulin syringes — one capped, one uncapped
Insulin syringes
  1. Tuberculin. Can be used to inject drugs, but are rarely used by PWID. Tuberculin syringes come in two pieces (with removable needles that slip on and off) and often have blue caps or blue slip-on needles.
Picture of a tuberculin syringe with the needle attached
Tuberculin syringe
  1. Intramuscular. Intramuscular (IM) syringes usually come in two pieces (with screw-on, “Luer Lock” needles). These syringes come in our injectable naloxone kits. IM syringes are not suitable for injecting drugs!

    You can usually tell if a syringe is for IM use if:
    • It holds more than 1 milliliter (mL) of liquid
    • It has a screw-on needle
    • The gauge (thickness) of the needle is 25G or lower (usually 18G – 25G)
Picture of an intramuscular (IM) syringe with unattached needle
Intramuscular syringe

Syringe Sizes

Syringes are measured in three ways:

  1. Needle length. Measured in inches (” or in.) or millimeters (mm). Typically comes in two sizes:
    • Shorts (5/16″ or 8 mm)
      • Better at reaching superficial (shallow) veins that are close to the skin
      • Easier to handle
    • Longs (1/2″ or 12.7 mm)
      • Ideal for reaching deeper veins
      • Usually work better than shorts if you’re dehydrated or cold
      • More difficult to handle

  2. Needle thickness. Measured in gauge (G) — the size of the hole (bore) of the syringe. Most PWID stay between 27G – 31G.
    • Lower Gauges (e.g., 27G)
      • Thicker needles
      • Leave larger puncture wounds in skin, thus a higher chance of infection
      • Usually causes more bleeding
      • Less likely to clog
      • Fills up with water faster
      • If you have to reuse syringes, lower gauges stay sharp longer
    • Higher Gauges (e.g., 31G)
      • Thinner needles
      • Leave smaller puncture wounds in skin, thus a lower chance of infection
      • Usually causes less bleeding
      • More likely to clog
      • Fills up with water slower
      • If you have to reuse syringes, higher gauges get dull faster

  3. Barrel size. Measured in milliliters, cubic centimeters, or units (1 mL = 1 cc = 100 units). Most PWID use 1-mL insulin syringes — these are by far the most common syringes used to inject drugs.
    • Smaller Sizes (e.g., 0.3 mL, 0.5 mL)
      • Generally easier to handle
      • Holds less water
      • Suitable for people who inject smaller doses
    • Larger Sizes (e.g., 1 mL)
      • Generally harder to handle, though most PWID have no trouble handling these
      • Holds more water
      • Suitable for people who inject larger doses
      • Better suited for drugs that need more water to dissolve (e.g., black tar heroin)